This artist's rendering provided by NASA shows the Curiosity rover on the surface of Mars. Photo: AP

Nasa officials have announced plans to build a new rover that would join Curiosity and Opportunity on the red planet's surface in 2020, potentially to collect soil or rock samples that could later be sent back to Earth.

The objectives are not yet set, nor are the tools the rover would wield, said John Grunsfeld, head of Nasa's Science Mission Directorate. But Grunsfeld's remarks on Tuesday raised the hopes of planetary scientists that Nasa is focusing its efforts on the complex and costly task of retrieving a piece of Mars.

"Collecting a cache of samples is difficult - it requires a very capable vehicle," said Steve Squyres, lead scientist for Opportunity rover, which landed on the planet in 2004. "The vehicle that John Grunsfeld just described for launch in 2020 is fully capable of doing that job."

The announcement electrified many of the roughly 18,000 researchers attending the American Geophysical Union's autumn meeting, taking place this week in San Francisco.

Before Curiosity landed on Mars this summer, Nasa was unsure of its future direction in exploring the solar system. Flagship missions to Mars seemed politically unpalatable after Curiosity's US$2.5 billion price tag, and no other major missions had been slated, even as the next launch window in 2018 fast approached.

But the rover's dramatic landing and early scientific exploits have rejuvenated enthusiasm for Martian exploration.

One idea for the new rover is for it to collect and store soil and rock samples, with a later mission bringing them back to Earth.

This article appeared in the South China Morning Post print edition as New Mars rover is planned by Nasa